目的　建立乳腺癌癌前期病变动物模型 ,探索外源性雌激素 (EE)及其拮抗剂的作用。方法　Wistar雌性大鼠 5 0只 ,对照组 12只 ;其余大鼠经胃管灌注 7,12 二甲基苯并蒽 (DMBA) ,8只用正常饮料 (DMBA组 ) ;15只饲料中加乙烯雌酚 (DMBA +DES组 ) ;15只饲料加三苯氧胺 (DMBA +TAM组 )。 3个月后检测乳腺增生、核仁形成区嗜银蛋白 (AgNOR)和DNA含量。结果　DMBA组和DMBA+DES组的乳腺组织增生率分别为 75 %及 93 33 % ;AgNOR计数为 3 71± 0 76及 5 6 0± 0 42 ;DNA含量为 88 5 9± 7 17及 137 75± 3 13,DMBA组及DMBA +DES组与对照组和DMBA +TAM组比较差异有显著意义 (P <0 0 1)。结论　一次性灌注DMBA可以建立乳腺癌癌前期病变动物模型 ;EE可加重DMBA诱导的乳腺癌癌前期病变 ;而TAM则具有阻断作用 Objective To establish an animal model of breast cancer precancerous lesions and explore the role of exogenous estrogen (EE) and its antagonists. Methods A total of 50 Wistar female rats were used in the control group and 12 rats in the control group. The remaining rats were treated with 7,12 dimethyl benzopyrene (DMBA) by gastric tube, 8 of them were in normal drink (DMBA group), and 15 of them were treated with ethylene. Estradiol (DMBA + DES group); 15 diets plus tamoxifen (DMBA + TAM group). Three months later, mammary gland hyperplasia, AgNOR and DNA content were detected. Results The rate of breast hyperplasia in DMBA group and DMBA+DES group was 75% and 93 33% respectively; AgNOR count was 3 71± 0 76 and 5 6 0± 0 42 ; DNA content was 88 5 9± 7 17 and 137 75 ± 3 13. There was significant difference between DMBA group and DMBA + DES group and control group and DMBA + TAM group (P <0 01). Conclusion One-time perfusion of DMBA can establish animal models of breast cancer precancerous lesions; EE can aggravate DMBA-induced breast cancer precancerous lesions; while TAM has blocking effect.